NEWTON — It’s well-documented the unique challenges Iowa Speedway presents IndyCar drivers, but there was another that reared its head repeatedly during a rainy practice and qualifying day Friday.

With the NASCAR Camping World Truck Series running in support of tonight’s Iowa Corn Indy 300, the differences in rubber between NASCAR’s Goodyear and IndyCar’s Firestone tires creates an unpredictable racetrack when the cars first hit the track.

“It’s definitely going to be a challenge,” said Tony Kanaan, who qualified second for Saturday’s race. “That’s always been a challenge for us here, or wherever we go and they race before us. It’s two different tire manufacturers, two different compounds. It makes it interesting in the beginning.”

The IndyCar drivers consistently hit the track after prolonged periods of time on track for the Truck Series, starting with the morning practice sessions, then both qualifying sessions.

But with the forecast looking like rain over night, there’s a possibility the IndyCars will start their race with a “green” racetrack, meaning all the rubber washed away and starting from scratch. Drivers prefer that situation to starting with Truck rubber laid down, as it’s a little easier to predict.

“A little bit of rain probably wouldn’t hurt, because it would take some of the surface off without too much of the base,” said defending race-winner James Hinchcliffe. “Either way, it’s going to be a great racetrack for us. The first hour will be in the sunlight.

“There’s going to be a lot of things that change and evolve.”

The driver and team who can best keep up with the track conditions is likely the one to end up racing for the win by race’s end.

Between possible rain and the different rubber, getting a head start can only help.

“The rain cleans the truck rubber off, and I think it would be better (starting) in those conditions,” said Helio Castroneves, who starts third in tonight’s race. “You’ve got to adjust the tools you have in the car, and expect something (different). And the toughest thing here is we’re talking about a 17-second lap time. You don’t have much luxury, if in the first stint your car is not very good to set up for the next one. It’s very important to at least have a decent start.”

Still, it’s not a death sentence to start off with an imperfect car.

Drivers like Hinchcliffe and Ryan Hunter-Reay will start deeper in the field than they’d like (13th and 14th respectively), and teammate Marco Andretti, who qualified eighth, felt he could’ve had a better lap with more ideal track conditions. Andretti said despite those frustrations and starting a bit behind the eight ball because of either a green track or Goodyear rubber buildup — depending on what happens overnight — can be overcome by the end of the night.

“There was just no rubber on the track, and with an early (qualifying) draw, you don’t even have a shot at pole,” Andretti said. “But it doesn’t matter (the conditions) because it’s 300 laps. Either way, the first stint we’re always prepared for an imbalance.”

The magnifying of handling issues because of how fast IndyCars go around Iowa Speedway — Scott Dixon’s pole-winning run Friday was 186.256 mph, 17.25 seconds — is also front and center on drivers’ minds.

Drivers said repeatedly the sensation of speed is likely the highest at Iowa Speedway because of just how fast they’re going in such a confined space. It’s a feeling they love, and lends itself to some great racing.

“It takes your eyes a minute to adjust to how fast everything happens here. It makes for an exciting race,” said Graham Rahal, who qualified 15th. “Other than maybe Pocono Turn One, this is the place that gives you the fastest sensation of speed.”

Dixon will lead the field to green, with the race set to start at 7:45 p.m., and felt a little more relief than happiness after winning the pole. He and his teammate Kanaan haven’t had the start to the season they’d wanted, and hope to make Iowa Speedway the turnaround point.

“I think in some areas, we know where we’ve missed. But what we can do now is go for race wins,” Dixon said. “It’s been a little while (since starting on pole), and it’s a nice feeling. The best thing is (Ganassi Racing) has three cars in the top four, and all four cars in the top seven, so that’s huge for us right now.”